Congestive heart failure is the largest unsolved problem in cardiac care today. The incidence of congestive heart failure (CHF) is increasing worldwide with over one million new cases diagnosed annually. There are over 5.5 million people in the United States with CHF diagnosis and the number of patients is expected to double over the course of this decade.
Treatment options for CHF are limited and fall into two categories; pharmacological and mechanical. The existing treatment options only relieve the clinical symptoms of CHF and ultimately, CHF patients treated with pharmacological therapies will degenerate into the terminal phase of end-stage heart failure, for which the only therapy is cardiac transplantation. Cardiac transplantations are limited by donor scarcity to only about 2,000 procedures per year. Due to the limitation of donor organs and a long waiting list, ventricular assist devices (VAD) were introduced as a bridge to transplantation.
A VAD may be generally described as a pump that assumes the function of a damaged ventricle of the heart by uploading ventricular volume while restoring blood flow to the vasculature. In the case of a VAD designed to assist the left ventricle in pumping blood from the heart, through the aorta to the rest of the body, implantation is achieved by cannulating the apex of the left ventricle and the aorta. The VAD then assists in pumping blood from the left ventricle, through the cannula, and to the aorta.
Although VADs have traditionally been used as a bridge for patients awaiting a heart transplant, more recently, they have been tested as an alternative to heart transplantation, and the FDA has granted limited approval to permanently implanting certain VADs in qualifying patients. When used as an alternative to a heart transplant, the focus of the treatment is to facilitate recovery by allowing the weakened heart to rest. It has been reported recently that, of a series of 12 patients supported by VAD, 11 patients had myocardial recovery, and the device was successfully explanted. See Tansley, P. and M. Yacoub, “Minimally invasive explanation of totally implantable left ventricular assist devices,” J. Thor. Card. Surg., 124:189-191, 2002.
Although the use of VADs as an alternative to heart transplantation is an exciting development, there are problems associated with VADs when used as an alternative to heart transplantation. For example, VADs are not designed to promote myocardial recovery and the implantation of VADs, which requires ventricular cannulation, often damages and creates loss of the myocardial tissue. For another example, aortic valve fusion can occur during chronic VAD implantation. For another example, VADs are designed to take over the pumping of blood and to do so in a continuous manner. As such, the VADs do not allow the heart to fill and eject a normal stroke volume (SV) or the amount of blood pumped by the left ventricle of the heart in one contraction. When the heart is kept from filling and ejecting a normal SV stiffening of the myocardium may result.
Another treatment option that has enjoyed some success for short-term treatment of cardiac dysfunction is counterpulsation therapy. One type of counterpulsation therapy involves removing blood from the aorta during native heart systole, thereby decreasing workload of the heart in ejecting blood, and returning the blood to the aorta as during diastole, while the heart is relaxing, thereby improving blood flow by supplying increased blood pressure during diastole. As such, counterpulsation has many important clinical benefits for the heart, including, decreased ventricular workload and increased coronary perfusion.
Counterpuslation therapy is typically provided with an intra-aortic balloon pump (IABP). Approximately 160,000 patients receive this treatment annually worldwide; however, the IABP has various disadvantages. For example, the IABP generally includes a balloon on a catheter, which catheter is introduced to the patient via a major groin artery, requiring a patient to remain supine and virtually immobilized for the duration of therapy, which results in additional complications such as muscle deterioration, clotting in the legs, and an increased risk of pneumonia. Furthermore, bacteria are found in large amounts in the groin area and bacteria may travel through the catheter and into the blood stream of the patient, causing infection. Additionally, there is a risk that the catheter introduced via the groin artery may result in blocked or substantially reduced blood flow to the patent's leg such that leg ischemia and even leg loss becomes a risk after only a few days. In any event, the application of IABP is limited to short durations, typically less than 14 days. Also, the ability to control and adjust the operation of the IABP is minimal. Accordingly, there remains a need in the art for a system and method which satisfactorily addresses the problems associated with known cardiac treatment options.